As is known, vane pumps of the above type are currently used for pumping various fluids, such as lubricating oil in an internal combustion engine.
In the present invention, operation of the pump is controlled by delivery pressure and a further parameter, e.g. oil temperature.
Pumping systems are known, in fact, which are controlled not only by the delivery pressure of the pump but also by oil temperature.
Two such control systems are described in U.S. Pat. No. 5,800,131 and FR-2 825 419, in which a member sensitive to variations in oil temperature acts directly on the pump ring to vary the eccentricity, and therefore displacement, of the pump as a function of lubricating oil temperature. More specifically, eccentricity (and therefore displacement) of the pump is increased by the control system as a function of the increase in oil temperature, to meet higher oil demand by the internal combustion engine.
Existing control systems of this type, however, have not proved altogether satisfactory, by subjecting the ring to severe forces that are difficult to control.